The present invention relates generally to steamer apparatus, and more particularly to novel convection type steamer apparatus which, in various embodiments, employ at least one oven chamber and a steam generator operative to provide steam to the oven chamber in a highly efficient, reliable and economical manner.
It is well known in the art of cooking to employ forced convection type steam ovens, generally termed steamers, to heat food items placed within a cooking chamber or compartment. The art of steam cooking was developed as an alternative to cooking food in a free or forced-convection hot air environment. Surface heat transfer coefficients associated with condensing saturated steam are typically greater than those of circulating hot air. Foods cooked in steam cook more quickly, retain their moisture better, maintain their food values, and are generally more pleasing in appearance. Conventional steamers surround food objects with a continuous supply of saturated steam.
Historically, tabletop type single oven chamber steamers have utilized atmospheric steam generators to supply steam to the oven chambers because of the smaller size of atmospheric steam generators over pressure boilers. However, a significant drawback to prior steamers having atmospheric steam generators is that they are slow in responding to a call for steam and in bringing the oven chamber to a desired cooking temperature. The delay in providing steam upon command is due to maintaining the temperature of the water in the steam generator at less than its boiling temperature, such as at a temperature of approximately 185.degree.-190.degree.. Thus, when responding to a demand for steam, as in a cooking cycle, the water in the boiler has to first be brought to its boiling temperature, and the oven chamber temperature then raised to a steam cooking temperature from a relatively cold condition. This can result in a delay of several minutes before actual cooking commences.
Prior double oven chamber steamers employ pressure boilers to supply steam to the oven chambers. A single pressure boiler supplies steam to both of the oven chambers through a valving arrangement. The double oven chambers are housed in an upstanding cabinet which has sufficient space beneath the oven chambers to accommodate a pressure boiler. Since pressure boilers maintain the heated boiler water under pressure, the heated boilers respond almost immediately to a demand for steam and are therefore faster than atmospheric steam generators in bringing the oven chambers to cooking temperatures. A drawback to pressure boilers is their relatively high cost. Also, as with prior single oven chamber steamers, the double oven chambers or cavities are relatively cold between cooking cycles and must be brought up to steam cooking temperatures, thus causing a time delay.
Significant improvements to prior single oven chamber steamers, and particularly tabletop type models having the capability to cook with steam or with dry oven heat, are disclosed in U.S. Pat. Nos. 4,851,644 and 4,817,582, both of which are owned by the assignee of the present invention and are incorporated herein by reference.
In both gas-fired and electrically heated steamers of known design, the steam is often introduced into the cooking chambers or cavities through relatively small orifices. These orifices frequently become clogged with lime buildup. Cleaning or deliming to clear the orifices is time consuming and leads to down time with attendant economic loss. Further, the boilers utilized in known steamers are such that cleaning or deliming solution must be introduced at the top of the boiler or by other means which are not easily accessible.